Floating floors incorporate an intervening sound isolating layer between the walking surface and the joists. Sound isolating materials that may be used are resiliently yielding materials such as foamed rubbers or mineral wool mats and create a partial discontinuity in the system which results in reduced sound transmission through the structure. The sound isolating layer may be a strip laid along the joists or a continuous layer of the material resting on a deck fixed on the joists. In the former case the walking surface is generally fixed to battens which rest on the strips. In the latter case two bonded layers of panel material with staggered joints are required in order to produce a stable walking surface. Examples of both types are described in Approved Document E1/2/3, "Airborne and Impact Sound", published by Her Majesty's Stationery Office, London, 1985.
In both cases the floating floor construction is thicker than a directly fixed walking surface by at least 30 mm. In situations where an existing floor is being upgraded this additional thickness can be a disadvantage, for example at door openings and stairheads.